1. Field of the Invention
The present invention relates to systems for filtering fluids in vehicles. More particularly, the present invention relates to a fluid filtration assembly combining return-side and supply-side filters to filter a circulating fluid as it enters and leaves a sump portion of a vehicle transmission.
2. Description of the Prior Art
As will be appreciated by those with ordinary skill in the automotive arts, an automatic transmission is a complex hydraulic circuit whose primary purpose is to allow an engine to operate in a narrow RPM (revolutions per minute) band while providing a wide range of output speeds. The transmission uses a fluid, typically a light oil, to create a hydraulic coupling that converts engine power to hydraulic pressure. The fluid serves other purposes as well, including lubrication and heat transfer. As it circulates through the transmission, the fluid collects damaging particulates such that it is desirable to filter the fluid at some point prior to recirculation. Commonly, fluid filtration takes place as the fluid is drawn back into circulation from a sump or reservoir.
Unfortunately, existing filtration systems suffer from a number of disadvantages. Filtering for small particulates, for example, as the fluid is drawn back into circulation creates a bottleneck effect that can result in undesirable drops in fluid pressure. This is of particular concern during cold flow conditions. Furthermore, because it alone provides all filtration, the single supply-side filter can clog when tasked to remove large amounts of contaminant, resulting in poor performance but for burdensomely frequent filter changes or cleanings.
It is known in the art to incorporate a spin-on filter to perform at least some filtration as the fluid enters the sump. Unfortunately, the nature and design of the spin-on filter is so substantially different from the typical supply-side filter that no interchangeability or shared structural components, desirable from a design and manufacturing standpoint, is possible. Furthermore, transmission designs are not easily adapted to accommodate the spin-on filter.
Due to the above-identified and other problems in the art, a need exists for an improved fluid filtration assembly or method.
The fluid filtration assembly of the present invention overcomes the above-identified and other problems in the art to provide a simple and inexpensive integrated assembly advantageously and efficiently accomplishing both return-side and supply-side filtration of a fluid as it enters and leaves a sump portion of a vehicle transmission. This two-stage filtration aids to mitigate or substantially eliminate bottleneck effects and fluid pressure drops at the supply-side.
The preferred fluid filtration assembly comprises a common housing component; a return-side filter; and a supply-side filter. The common housing component provides a substantial advantage in that it allows for design and manufacturing efficiencies not possible with existing spin-on filter technology. Furthermore, by sharing the common housing component, be it a bottom, top, or side wall, the return-side and supply-side filters are integrated into a single fluid filtration assembly conveniently locatable in the sump where it is easily accessed for maintenance. Additionally, the common housing component facilitates the direct flow embodiment described below.
The return-side filter is operable to filter at least a portion of the fluid as it enters or returns to the sump, with any remaining fluid flowing directly into the sump. The return-side filter includes a return-side filter media operable to filter both large and relatively small particulates, and may also include a magnet operable to trap and hold metal particles or shavings that would otherwise prematurely clog the filter media. Fluid flow through the return-side filter may be accomplished using any of three alternative embodiments, including upflow, downflow, and direct feed configurations. In the upflow embodiment, the fluid enters beneath and rises through the return-side filter media to exit at or near the top of the return-side filter and empty into the sump. One advantage of the upflow embodiment is that particulates are allowed to settle out of the fluid before exposure to the filter media, thereby extending the filter media""s operational life. In the downflow embodiment, the fluid enters above and flows downward through the return-side filter media to exit at or near the bottom of the return-side filter and empty into the sump. In the direct flow embodiment, regardless of where the fluid enters or how it is filtered within the return-side filter, the filtered fluid thereafter flows directly to the supply-side filter rather than into the sump.
The supply-side filter receives fluid either from the sump, directly from the return-side filter, or some combination thereof, filters the fluid again, and then releases the fluid back into circulation. Because a substantial amount of undesirable particulates are removed from the fluid by the return-side filter media, possibly aided by the settling action of the upflow embodiment, the supply-side filter media can be a low-restriction filter media operable to remove only relatively large particulates, which advantageously decreases bottle-neck effects and minimizes fluid pressure drops.
These and other important features of the present invention are more fully described in the section titled DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT, below.